1. Field of the Invention
The present invention relates to a projection lens unit of a projector and a projector.
2. Description of the Related Art
A projector projects light, which is applied to an image forming panel from a light source, onto a projection surface through a projection lens unit to display an image. In a recent projector, the illuminance of a projected image has been further improved through the improvement of an image forming panel and a light source than in the related art. As a result, unnecessary light, which does not contribute to the formation of an image, is also increased, and the temperature of a lens barrel of a projection lens unit becomes higher than that in the related art in a case in which the unnecessary light is removed by the lens barrel or a light screen of the projection lens unit.
In a projector disclosed in JP2005-128217A, a reflective region is provided on a portion, which receives unnecessary light, of a lens holder, a stop, or the like of a lens barrel and the absorption of unnecessary light is suppressed. Accordingly, a rise in the temperature of the lens barrel is suppressed, so that the deformation of the lens barrel caused by a rise in temperature is suppressed.
In a projector disclosed in JP2014-59333A, an unnecessary light-receiving member overlaps with a lens holder of a lens barrel, and the surface of a contact portion of the lens holder, which is in contact with the unnecessary light-receiving member, is formed in an uneven shape. Accordingly, the transfer of heat to the lens holder from the unnecessary light-receiving member is reduced in comparison with a case in which the entire surface of the unnecessary light-receiving member is in contact with the lens holder. Therefore, a rise in the temperature of the lens barrel is suppressed, so that the deformation of the lens barrel caused by a rise in temperature is suppressed.
Further, the following projectors are known. The projectors are adapted to displace a lens group, which is held by a holding member, in the direction of an optical axis through the thermal expansion of the holding member holding some lenses of a lens barrel against the change of a focal position, which occurs due to the deformation of the lens barrel caused by heat, to correct the change of the focal position (for example, JP2009-271448A and JP2012-242728A).